Effect of polyphenols against complications of COVID-19: current evidence and potential efficacy

The COVID-19 pandemic that started in 2019 and resulted in significant morbidity and mortality continues to be a significant global health challenge, characterized by inflammation, oxidative stress, and immune system dysfunction.. Developing therapies for preventing or treating COVID-19 remains an important goal for pharmacology and drug development research. Polyphenols are effective against various viral infections and can be extracted and isolated from plants without losing their therapeutic potential. Researchers have developed methods for separating and isolating polyphenols from complex matrices. Polyphenols are effective in treating common viral infections, including COVID-19, and can also boost immunity. Polyphenolic-based antiviral medications can mitigate SARS-CoV-2 enzymes vital to virus replication and infection. Individual polyphenolic triterpenoids, flavonoids, anthraquinonoids, and tannins may also inhibit the SARS-CoV-2 protease. Polyphenol pharmacophore structures identified to date can explain their action and lead to the design of novel anti-COVID-19 compounds. Polyphenol-containing mixtures offer the advantages of a well-recognized safety profile with few known severe side effects. However, studies to date are limited, and further animal studies and randomized controlled trials are needed in future studies. The purpose of this study was to review and present the latest findings on the therapeutic impact of plant-derived polyphenols on COVID-19 infection and its complications. Exploring alternative approaches to traditional therapies could aid in developing novel drugs and remedies against coronavirus infection.

The effect of oral supplementation of Paricalcitol on C-reactive protein levels in chronic kidney disease patients: GRADE-assessed systematic review and dose-response meta-analysis of data from randomized controlled trials

BACKGROUND

Previous studies investigating the effect of oral supplementation of paricalcitol on reactive protein levels in chronic kidney disease (CKD) patients reported inconsistent findings. In this systematic review and meta-analysis, we have analyzed and interpreted the results obtained from previous randomized clinical trials on the effect of paricalcitol on C-reactive protein in CKD patients in the literature.

METHODS

MEDLINE, SciVerse Scopus, and Clarivate Analytics Web of Science databases were searched until January 2023 and related articles were obtained through a careful screening process allowing extraction of required data from selected articles. The effect size was calculated using a random effect model and weighted mean differences (WMD) and 95% confidence intervals (CI). Heterogeneity among studies was evaluated using Cochran's Q test and I2.

RESULTS

Amongst the 182 articles obtained from the initial search, 4 studies (6 arms) were finally included in the meta-analysis. Pooled analysis shows that C-reactive protein levels significantly decrease after oral supplementation with paricalcitol (WMD: -2.55 mg/L, 95% CI (-4.99 to -0.11; P = 0.04). The studies used in this meta-analysis showed significant heterogeneity (I2 = 66.3% and P = 0.01).

CONCLUSION

Oral paricalcitol supplementation in CKD patients can significantly reduce C-reactive protein levels, which may prevent CKD progression.

Curcumin Nanofibers: A Novel Approach to Enhance the Anticancer Potential and Bioavailability of Curcuminoids

Development of novel treatment methods for cancer is needed given the limitations of current treatment methods, including side effects and chemotherapeutic resistance, which may provide new hope to cancer patients. Cancer is the second leading cause of global mortality. Curcumin, the active ingredient of turmeric, has been used since ancient times for various therapeutic purposes. Several studies have identified its activity against cancer. Despite the established anticancer activity of curcumin, its low aqueous solubility and bioavailability are barriers to its effectiveness. In an attempt to solve this problem, many studies have formulated curcumin nanofiber preparations using a variety of methods. Electrospinning is a simple and affordable method for the production of nanofibers. Studies have shown increased curcumin bioavailability in nanofibers resulting from their high surface/volume ratio and porosity. We have undertaken a detailed review of studies on the anticancer effects of curcumin nanofibers. Curcumin acts by inhibiting various biological cancer pathways, including NF-κB, mTOR, complex I, cytokines, expression of p-p65, Ki67, and angiogenesis-associated genes. It also induces apoptosis through activation of caspase pathways and ROS production in cancer cells. Curcumin-loaded PLA50/PVP50/Cur15 nanofibers were investigated in breast cancer, one of the most studied cancers, and was shown to have significant effects on the widely used HeLa-cell line. Most of the studies undertaken have been performed in cell lines in vitro, while relatively few animal studies have been reported. More preclinical and clinical studies are needed to evaluate the anticancer activity of curcumin nanofibers. Amongst studies undertaken, a variety of curcumin nanofibers of various formulations have been shown to suppress a variety of cancer types. Overall, curcumin nanofibers have been found to be more efficient than free curcumin. Thus, curcumin nanofibers have been observed to improvise cancer treatment, offering great potential for effective cancer management. Further studies, both in vitro and in vivo, involving curcumin nanofibers have the potential to benefit cancer management.

Impact of Phytochemicals on PPAR Receptors: Implications for Disease Treatments

Peroxisome proliferator-activated receptors (PPARs) are members of the ligand-dependent nuclear receptor family. PPARs have attracted wide attention as pharmacologic mediators to manage multiple diseases and their underlying signaling targets. They mediate a broad range of specific biological activities and multiple organ toxicity, including cellular differentiation, metabolic syndrome, cancer, atherosclerosis, neurodegeneration, cardiovascular diseases, and inflammation related to their up/downstream signaling pathways. Consequently, several types of selective PPAR ligands, such as fibrates and thiazolidinediones (TZDs), have been approved as their pharmacological agonists. Despite these advances, the use of PPAR agonists is known to cause adverse effects in various systems. Conversely, some naturally occurring PPAR agonists, including polyunsaturated fatty acids and natural endogenous PPAR agonists curcumin and resveratrol, have been introduced as safe agonists as a result of their clinical evidence or preclinical experiments. This review focuses on research on plant-derived active ingredients (natural phytochemicals) as potential safe and promising PPAR agonists. Moreover, it provides a comprehensive review and critique of the role of phytochemicals in PPARs-related diseases and provides an understanding of phytochemical-mediated PPAR-dependent and -independent cascades. The findings of this research will help to define the functions of phytochemicals as potent PPAR pharmacological agonists in underlying disease mechanisms and their related complications.

Ginger and its constituents: Role in treatment of inflammatory bowel disease

Inflammatory bowel diseases (IBD), with obscure etiology, are rising and are of worldwide concern. Of the various components of IBD pathogenesis and progression, irritation appears to play a major part. Investigations on the molecular and cellular pathways that activate the IBD provide the focus for the development of useful therapies. Ginger (the rhizome of Zingiber officinale) has a broad spectrum of clinical applications due to its anti-inflammatory and anti-oxidative functions. Inflammation and oxidative stress are the key pathogenic factors in many diseases, including IBD. The most established components of ginger are phenolic compounds called gingerols. A wide range of pharmacological activities of the potential therapeutic benefit of Z. officinale have been detailed. In this regard, the anti-inflammatory activity of ginger has been documented by many researchers. It was shown that ginger is a potent inhibitor of the nuclear factor kappa B (NF-κB), signal transducer of activators of transcription (STATs), Nod-like receptor family proteins (NLRPs), toll-like receptors (TLRs), mitogen-activated protein kinase (MAPKs), and mTOR (mTOR) pathways, as well as inhibiting various pro-inflammatory cytokines. In the present report, the potential application of ginger in the management of IBD is reviewed in detail, with an emphasis on the relevant properties of ginger and its bioactive components. The significance of the functions, side effects, and delivery of ginger to the digestive system for particular application in IBD are also considered.

Impact of Curcumin on Microsomal Enzyme Activities: Drug Interaction and Chemopreventive Studies

Curcumin, a yellow pigment in Asian spice, is a natural polyphenol component of Curcuma longa rhizome. Curcuminoid components include curcumin, demethoxycurcumin (DMC), and bisdemethoxycurcumin (BDMC). Previous studies established curcumin as a safe agent based on preclinical and clinical evaluations and curcuminoids have been approved by the US Food and Drug Administration (FDA) as "Generally Recognized as Safe" (GRAS). The present review collects and summarizes clinical and preclinical studies of curcumin interactions, with an emphasis on the effect of curcumin and curcumin analogs on the mRNA and protein levels of microsomal CYP450 enzymes (phase I metabolism) and their interactions with toxicants, drugs and drug probes. The literature search was conducted using keywords in various scientific databases, including Web of Science, Scopus, PubMed, and Google Scholar. Studies concerning the impact of curcumin and curcumin analogs on microsomal enzyme activity are reviewed and include oral, topical, and systemic treatment in humans and experimental animals, as well as studies from in vitro research. When taken together the data identified some inconsistent results between various studies. The findings showed significant inhibition of CYP450 enzymes by curcumin and its analogs. However such effects often differed when curcumin and curcumin analogs were coadministered with toxicant and other drugs and drug probes. We conclude from this review that herb-drug interactions should be considered when curcumin and curcumin analogs are consumed.

Resveratrol: Mechanistic and therapeutic perspectives in pulmonary arterial hypertension

Resveratrol, trans 3,5,4'-trihydroxystilbene, is a stilbenoid polyphenol with a wide range of properties including antioxidant, neuroprotective, cardioprotective, anti-inflammatory and anticancer activities. It is found in the skins of grape (50-100 μg/mL), red wine, peanuts, bilberries, blueberries and cranberries. The most important effects of resveratrol have been found in cardiovascular disease, with pulmonary arterial hypertension (PAH) being a major severe and progressive component. Many factors are involved in the pathogenesis of PAH, including enzymes, transcription factors, proteins, chemokines, cytokines, hypoxia, oxidative stress and others. Resveratrol treats PAH through its actions on various signaling pathways. These signaling pathways are mainly suppressed SphK1-mediated NF-κB activation, BMP/SMAD signaling pathway, miR-638 and NR4A3/cyclin D1 pathway, SIRT1 pathway, Nrf-2, HIF-1 α expression, MAPK/ERK1 and PI3K/AKT pathways, and RhoA-ROCK signaling pathway. Resveratrol efficiently inhibits the proliferation of pulmonary arterial smooth muscle cells and right ventricular remodeling, which are underlying processes leading to enhanced PAH. While supportive evidence from randomized controlled trials is yet to be available, current in vitro and in vivo studies seem to be convincing and suggest a therapeutic promise for the use of resveratrol in PAH.

Interactions between antidiabetic drugs and herbs: an overview of mechanisms of action and clinical implications

Diabetes is a complex condition with a variety of causes and pathophysiologies. The current single target approach has not provided ideal clinical outcomes for the treatment of the disease and its complications. Herbal medicine has been used for the management of various diseases such as diabetes over centuries. Many diabetic patients are known to use herbal medicines with antidiabetic properties in addition to their mainstream treatments, which may present both a benefit as well as potential risk to effective management of their disease. In this review we evaluate the clinical and experimental literature on herb-drug interactions in the treatment of diabetes. Pharmacokinetic and pharmacodynamic interactions between drugs and herbs are discussed, and some commonly used herbs which can interact with antidiabetic drugs summarised. Herb-drug interactions can be a double-edged sword presenting both risks (adverse drug events) and benefits (through enhancement). There is a general lack of data on herb-drug interactions. As such, more rigorous scientific research is urgently needed to guide clinical practice as well as to safeguard the wellbeing of diabetes patients.

An ethnopharmacological approach to the preliminary screening of native Australian herbal medicines for anticancer activity

BACKGROUND

Five plants used traditionally by Australian Aboriginals and two edible native Australian fruits have been investigated for anticancer activity. The aim was to identify native Australian herbal medicines which displayed anticancer activity, with cytotoxicity to cancer cells but sparing or even proliferating normal immunological cells, and subsequently provide potentially new anticancer drug leads.

METHODS

Extracts and derived fractions were assayed for cell viability against a multiple myeloma cell line, RPMI-8226, in comparison to the peripheral blood mononuclear cells (PBMC) representing normal human immunological cells.

RESULTS

None of the crude extracts exhibited the desirable differential activity; however, following further fractionation of the Eremophila duttonii F. Muell. (Myoporaceae) extract, one fraction (termed F01) exhibited a greater cytotoxicity to the cancer cell line than to the normal cells.

CONCLUSIONS

One fraction may potentially contain valuable compounds which may be useful for further investigation. This may focus on the identification of the bioavailable purified compounds present within these fractions or by detailed delineation of the related mechanisms of action.

Natural Products: Biochemical-Chemical Characterization, and Evidence for Therapeutic Potential

This Special Issue follows from a previous Issue entitled “Mechanism-Based Development of Natural Products for Human Health” arising from an inaugural conference on Natural Products Development held at Whistler Mountain, Canada from September 21-22, 2012. The timeliness of this issue reflects the continued growth in Natural Product research and the success of the First Issue, as judged from feedback we received and citations received. We were also encouraged by the interest in natural products research in recent years, as exemplified by the recent publication on Traditional Medicine in the prestigious journal Science (1, 2).

Preventative effect of Zingiber officinale on insulin resistance in a high-fat high-carbohydrate diet-fed rat model and its mechanism of action

Insulin resistance is a core component of metabolic syndrome and usually precedes the development of type 2 diabetes mellitus. We have examined the preventative effect of an ethanol extract of ginger (Zingiber officinale, Zingiberaceae) on insulin resistance in a high-fat high-carbohydrate (HFHC) diet-fed rat model of metabolic syndrome. The HFHC control rats displayed severe insulin resistance, whilst rats treated with ginger extract (200 mg/kg) during HFHC diet feeding showed a significant improvement of insulin sensitivity using the homeostatic model assessment of insulin resistance (HOMA-IR) after 10 weeks (p < 0.01). An in vitro mechanistic study showed that (S)-[6]-gingerol, the major pungent phenolic principle in ginger, dose-dependently (from 50 to 150 μM) increased AMPK α-subunit phosphorylation in L6 skeletal muscle cells. This was accompanied by a time-dependent marked increment of PGC-1α mRNA expression and mitochondrial content in L6 skeletal muscle cells. These results suggest that the protection from HFHC diet-induced insulin resistance by ginger is likely associated with the increased capacity of energy metabolism by its major active component (S)-[6]-gingerol.

(S)-[6]-Gingerol enhances glucose uptake in L6 myotubes by activation of AMPK in response to [Ca2+]i

PURPOSE

The aim of this study was to investigate the mechanism of (S)-[6]-gingerol in promoting glucose uptake in L6 skeletal muscle cells.

METHODS

The effect of (S)-[6]-gingerol on glucose uptake in L6 myotubes was examined using 2-[1,2-3H]-deoxy-D-glucose. Intracellular Ca2+ concentration was measured using Fluo-4. Phosphorylation of AMPKα was determined by Western blotting analysis.

RESULTS

(S)-[6]-Gingerol time-dependently enhanced glucose uptake in L6 myotubes. (S)-[6]-Gingerol elevated intracellular Ca2+ concentration and subsequently induced a dose- and time-dependent enhancement of threonine172 phosphorylated AMPKα in L6 myotubes via modulation by Ca2+/calmodulin-dependent protein kinase kinase.

CONCLUSION

The results indicated that (S)-[6]-gingerol increased glucose uptake in L6 skeletal muscle cells by activating AMPK. (S)-[6]-gingerol, a major component of Zingiber officinale, may have potential for development as an antidiabetic agent.

Light-to-moderate ethanol feeding augments AMPK-α phosphorylation and attenuates SREBP-1 expression in the liver of rats

PURPOSE

Fatty liver disease, a hepatic manifestation of metabolic syndrome, is one of the major causes of chronic liver diseases. Epidemiological studies suggest that regular light-to-moderate ethanol consumption lowers the risk of developing metabolic disorders including dislipidemia, insulin resistance, type 2 diabetes and fatty liver disease. However, the mechanism(s) of the protective effect of light-to-moderate ethanol consumption on the liver remains unknown.

METHODS

In the present study, we investigated the effects of light (6%, 0.94 g/kg/day) and moderate (12%, 1.88 g/kg/day) ethanol feeding in rats for 3 weeks on the circulating and hepatic biochemical profiles and on the hepatic protein expression and phosphorylation status of adenosine monophosphate-activated protein kinase-α (AMPK-α) and other down-stream targets of this enzyme including sterol regulatory element-binding protein-1 (SREBP-1), SREBP cleavage-activating protein (SCAP) and 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMG-CoA reductase).

RESULTS

Despite no significant difference in food-intake among the groups, light ethanol treatment significantly increased the body weight compared to control rats. Serum glucose, insulin, total cholesterol, triglycerides, phospholipids and hepatic cholesterol and triglycerides were not significantly different among the groups. However, serum free fatty acids were significantly reduced with light ethanol treatment. Both light and moderate ethanol treatment significantly increased the hepatic levels of phosphorylated AMPK-α protein and this was associated with significant reduction of SREBP-1 protein expression, suggesting an enhanced fatty acid oxidation. In addition, light ethanol treatment significantly decreased the SCAP protein expression in the liver. However, liver HMG-CoA protein expression was not significantly different with ethanol consumption.

CONCLUSION

Chronic light-to-moderate ethanol consumption increased AMPK activation which was associated with decreased expression of SREBP-1 and SCAP in the liver. Thus, our studies provide mechanistic evidence for the earlier epidemiological studies that indicate light-to-moderate ethanol intake lowers the risk of development of fatty liver disease and other metabolic disorders. Our studies demonstrate that the protective effects of light-to-moderate ethanol arise at least in part by increased phosphorylation of AMPK-α and decreased SREBP-1 expression in the liver. Further studies are warranted to determine the effects of light-to-moderate ethanol on intracellular up-stream and down-stream targets of AMPK and also on the implications of light-to-moderate ethanol in protecting non-alcoholic fatty liver disease.

Management of cardiorenal metabolic syndrome in diabetes mellitus: a phytotherapeutic perspective

Cardiorenal syndrome (CRS) is a complex disease in which the heart and kidney are simultaneously affected and their deleterious declining functions are reinforced in a feedback cycle, with an accelerated progression. Although the coexistence of kidney and heart failure in the same individual carries an extremely bad prognosis, the exact cause of deterioration and the pathophysiological mechanisms underlying the initiation and maintenance of the interaction are complex, multifactorial in nature, and poorly understood. Current therapy includes diuretics, natriuretic hormones, aquaretics (arginine vasopressin antagonists), vasodilators, and inotropes. However, large numbers of patients still develop intractable disease. Moreover, the development of resistance to many standard therapies, such as diuretics and inotropes, has led to an increasing movement toward utilization and development of novel therapies. Herbal and traditional natural medicines may complement or provide an alternative to prevent or delay the progression of CRS. This review provides an analysis of the possible mechanisms and the therapeutic potential of phytotherapeutic medicines for the amelioration of the progression of CRS.

Compound K modulates fatty acid-induced lipid droplet formation and expression of proteins involved in lipid metabolism in hepatocytes

BACKGROUND & AIMS

A key factor in the development of type 2 diabetes and non-alcoholic fatty liver disease (NAFLD) is hepatic steatosis. Incubation of human hepatic cells with free fatty acids (FFAs) causes accumulation of neutral lipids in lipid droplets (LDs) and serves as a model for hepatic steatosis. Ginsenosides, active constituents of ginsengs, have demonstrated beneficial effects in various pharmacological areas, including diabetes, however their effect on lipid accumulation in hepatocytes remains unclear. Here, we examine the effect of compound K (ComK), an active metabolite of ginsenosides, on the regulation of LD formation and on the expression of proteins involved in lipid homeostasis in hepatocytes.

METHODS

HuH7 cells were pretreated with ComK, followed by lipid loading with FFA. LDs were visualized using Oil Red O staining and immunohistochemistry for the LD-related protein PLIN2. Triglyceride levels were determined in isolated LDs. The expression of proteins involved in lipid homeostasis was examined by Western blotting.

RESULTS

Treatment with ComK significantly decreased LD formation in FFA-loaded HuH7 cells and increased phosphorylation levels of AMPK, and its substrate ACC. ComK also increased protein expression of peroxisome proliferator-activated receptor-α (PPAR-α) and acyl-CoA oxidase (ACOX1) together with elevated activity of a PPAR-α response element reporter construct. These effects were inhibited by the PPAR-α antagonist MK886.

CONCLUSIONS

ComK reduced LD formation and TG accumulation in FFA-loaded hepatocytes, in part by up-regulating AMPK activity and PPAR-α related pathways. These results suggest that ComK may have efficacy for the treatment of hepatic steatosis and associated diseases.

INTRODUCTION - Mechanism-based Development of Natural Products for Human Health

This Special Issue of the Journal of Pharmacy and Pharmaceutical Sciences arises from an inaugural conference on “Mechanism-Based Natural Product Development” held at Whistler Mountain, Canada on September 21-22, 2012. The aim of the conference was to bring together scientists from various disciplines to discuss the development of new therapeutic products from natural medicines based on mechanistic and related scientific studies. It provided an opportunity to explore new directions in natural medicine research and development, with the ultimate objective of leading to greater integration of natural and conventional synthetic pharmaceutical medicines for the health of the community worldwide. The concept for this conference and the Special Issue has come from the growing interest internationally in traditional and natural medicinal health products in recent years. It may, at first, appear surprising that developed countries are re-embracing natural product research and development. There are of course many reasons for this, including growing community interest in natural products providing improved health and wellbeing, the growing difficulty and cost of maintaining a pipeline of effective and, above all, safe new products for chronic diseases in the mainstream pharmaceutical industry, and the knowledge that many of our small drug pharmaceutical medicines have come from plants and other organisms. But as traditional natural product medicines increasingly enter the mainstream, the call for evidence to support their use also grows louder. Essential to the acceptance of natural medicines are the validation of their traditional uses and identification, isolation and structural characterization of their active components, together with the elucidation of their mechanisms of biological action, adverse effects, and identification of their molecular targets. These requirements provide the focus of this Special Issue. Scientific investigation and development of new health products requires the joining together of many disciplines, including chemistry, pharmacology, pharmacognosy and cell and molecular biology, as well as integration with clinical medicine. Natural product medicines are expected to be multi-component and multi-targeted. Are they effective, safe and properly standardized in their existing formulations? Are there opportunities to isolate single active components for standardization and conventional drug discovery and development? Answering these questions requires collaboration between scientific disciplines focused on a common goal. In line with the aims of the conference, the Special Issue has incorporated review and original research articles related to mechanisms of action in a number of therapeutic areas, mostly from invited speakers at the Whistler conference. Other articles were unsolicited submissions to the Journal that satisfy the scope of the issue. Articles range from reports on efforts to work with traditional owners in the appropriate cultural context, to develop new therapeutics based on traditional literature, to discover new medicinal products, to develop new pharmaceuticals based on the isolation of active chemical components, to develop new methods of delivery, and to identify mechanisms of action. The medical 'territory' includes cancer, heart disease, diabetes and related chronic inflammatory diseases, pain pathways, deafness and infertility. Other articles investigate the quality and safety of products by the application of current analytical methods, the potential for interactions of natural products (e.g., cranberry) with pharmaceutical medicines and the variability of a selection of similar natural product medicines with regard to their contents of therapeutically beneficial and marker compounds, as claimed on the product labels. In addition, the issue includes the abstracts of posters that formed an important part of the conference, especially from postgraduate students and postdoctoral fellows. These are included as Proceedings. We are indebted to the scientists who willingly gave their time and resources to attend the Whistler conference and, in many cases, submitted manuscripts for inclusion in this Special Issue. The delegates and contributors came from many places, near and far, to make this inaugural conference on mechanism-based natural product development a success. Such a conference and the subsequent proceedings in the Special issue are not possible without the work of many. We thank the organizing and scientific committee for their support and valuable suggestions. A conference of this scope would not be possible without sponsorship; this includes especially the National Health Products Research Society of Canada, the Canadian Society for Pharmaceutical Sciences and several Universities. Major support, without program or editorial input, was provided by SOHO Flordis International (SFI). We commend them for believing in the quest for clinically proven and research-based products based on an understanding of underlying mechanisms. The support of Purapharm International is also gratefully acknowledged. We would like to dedicate this Special Issue to Professor Allan SY Lau of the University of Hong Kong, who contributed enthusiastically to the organization of the conference and its program, but was ultimately unable to attend due to his untimely passing. Professor Lau was a pioneer in the integration of natural and orthodox medical studies and his inspiration will be greatly missed. Basil D Roufogalis, Arthur D Conigrave and Emanuel E Strehler Co-Guest Editors

Proceedings of conference on Mechanism-Based Development of Natural Products for Human Health

Mechanism-Based Development of Natural Products in Human Health

Evidence-based toxicity evaluation and scheduling of Chinese herbal medicines

ETHNOPHARMACOLOGICAL RELEVANCE

While there is an increasing number of toxicity report cases and toxicological studies on Chinese herbal medicines, the guidelines for toxicity evaluation and scheduling of Chinese herbal medicines are lacking.

AIM

The aim of this study was to review the current literature on potentially toxic Chinese herbal medicines, and to develop a scheduling platform which will inform an evidence-based regulatory framework for these medicines in the community.

MATERIALS AND METHODS

The Australian and Chinese regulations were used as a starting point to compile a list of potentially toxic herbs. Systematic literature searches of botanical and pharmaceutical Latin name, English and Chinese names and suspected toxic chemicals were conducted on Medline, PubMed and Chinese CNKI databases.

RESULTS

Seventy-four Chinese herbal medicines were identified and five of them were selected for detailed study. Preclinical and clinical data were summarised at six levels. Based on the evaluation criteria, which included risk-benefit analysis, severity of toxic effects and clinical and preclinical data, four regulatory classes were proposed: Prohibited for medicinal usage, which are those with high toxicity and can lead to injury or death, e.g., aristolochia; Restricted for medicinal usage, e.g., aconite, asarum, and ephedra; Required warning label, e.g., coltsfoot; and Over-the-counter herbs for those herbs with a safe toxicity profile.

CONCLUSION

Chinese herbal medicines should be scheduled based on a set of evaluation criteria, to ensure their safe use and to satisfy the need for access to the herbs. The current Chinese and Australian regulation of Chinese herbal medicines should be updated to restrict the access of some potentially toxic herbs to Chinese medicine practitioners who are qualified through registration.

Identification and characterisation of the RalA-ERp57 interaction: evidence for GDI activity of ERp57

RalA is a membrane-associated small GTPase that regulates vesicle trafficking. Here we identify a specific interaction between RalA and ERp57, an oxidoreductase and signalling protein. ERp57 bound specifically to the GDP-bound form of RalA, but not the GTP-bound form, and inhibited the dissociation of GDP from RalA in vitro. These activities were inhibited by reducing agents, but no disulphide bonds were detected between RalA and ERp57. Mutation of all four of ERp57’s active site cysteine residues blocked sensitivity to reducing agents, suggesting that redox-dependent conformational changes in ERp57 affect binding to RalA. Mutations in the switch II region of the GTPase domain of RalA specifically reduced or abolished binding to ERp57, but did not block GTP-specific binding to known RalA effectors, the exocyst and RalBP1. Oxidative treatment of A431 cells with H₂O₂ inhibited cellular RalA activity, and the effect was exacerbated by expression of recombinant ERp57. The oxidative treatment significantly increased the amount of RalA localised to the cytosol. These findings suggest that ERp57 regulates RalA signalling by acting as a redox-sensitive guanine-nucleotide dissociation inhibitor (RalGDI).

Fruit juices as perpetrators of drug interactions: the role of organic anion-transporting polypeptides

Grapefruit juice is widely recognized to cause important drug interactions via inhibition of CYP3A4, and a wider variety of fruit juices have been shown to inhibit influx transporters in enterocytes known as organic anion-transporting polypeptides (OATPs). Fruit juice coadministration significantly reduces the oral bioavailability of numerous important medicines relying on this anion transporter pathway for absorption. This article reviews the current literature on interactions between clinically used OATP substrates and fruit juice consumption.

Protein kinase C modulation of thermo-sensitive transient receptor potential channels: Implications for pain signaling

A variety of molecules are reported to be involved in chronic pain. This review outlines the specifics of protein kinase C (PKC), its isoforms and their role in modulating thermo-sensitive transient receptor potential (TRP) channels TRPV1-4, TRPM8, and TRPA1. Anatomically, PKC and thermo-sensitive TRPs are co-expressed in cell bodies of nociceptive dorsal root ganglion (DRG) neurons, which are used as physiological correlates of peripheral and central projections involved in pain transmission. In the past decade, modulation of painful heat-sensitive TRPV1 by PKC has received the most attention. Recently, PKC modulation of other newly discovered thermo-sensitive pain-mediating TRPs has come into focus. Such modulation may occur under conditions of chronic pain resulting from nerve damage or inflammation. Since thermo-TRPs are primary detectors of acute pain stimuli, their modulation by PKC can severely alter their function, resulting in chronic pain. Comprehensive knowledge of pain signaling involving interaction of specific isoforms of PKC with specific thermo-sensitive TRP channels is incomplete. Such information is necessary to dissect out modality specific mechanisms to better manage the complex polymodal nature of chronic pain. This review is an attempt to update the readers on current knowledge of PKC modulation of thermo-sensitive TRPs and highlight implications of such modulation for pain signaling

Methodologies for investigating natural medicines for the treatment of nonalcoholic fatty liver disease (NAFLD)

Non-alcoholic fatty liver disease (NAFLD) is emerging as a prominent condition in Western countries. In this review we describe the characteristics and current treatments of NAFLD and discuss opportunities for developing new therapeutic management approaches, with a particular emphasis on development of animal studies and in vitro assays for identification of components of natural product medicines. The main manifestation of NAFLD is hepatic lipid accumulation in the form of lipid droplets (LDs), known as hepatic steatosis (fatty liver). Current treatments for NAFLD generally aim to reduce triglyceride (TG) accumulation, often utilizing thiazolidinedines (TZDs) and fibrates, which are known to lower TG levels in hyperlipidemia, diabetes and metabolic syndrome. Both of these compounds act through activation of nuclear receptors of the Peroxisome Proliferator-Activated Receptor (PPAR) family, thereby activating genes involved in triglyceride metabolism. Thus treatment using natural PPAR α and PPAR γ ligands, such as polyunsaturated fatty acids (PUFA), has also been considered. Alternatively, natural medicines for the treatment of NAFLD have a long and successful history of controlling disease without prominent side effects. However, active compounds in natural medicine responsible for lowering hepatic TG levels are yet poorly characterized. This points to the need for medium-high throughput screening assays to identify active components within natural herbs. As outlined in this review, the quantification of the size and number of lipid droplets could provide an opportunity to screen compound libraries derived from natural medicine for their potential to reduce NAFLD.

Gingerols of Zingiber officinale enhance glucose uptake by increasing cell surface GLUT4 in cultured L6 myotubes

In this study we investigate the active constituents of the rhizome of Zingiber officinale, Roscoe (ginger) and determine their activity on glucose uptake in cultured L6 myotubes and the molecular mechanism underlying this action. Freeze-dried ginger powder was extracted with ethyl acetate (1 kg/3 L) to give the total ginger extract, which was then separated into seven fractions, consisting of nonpolar to moderately polar compounds, using a short-column vacuum chromatographic method. The most active fraction (F7) was further purified for identification of its active components. The effect of the extract, fractions, and purified compounds on glucose uptake was evaluated using radioactive labelled 2-[1,2-³H]-deoxy-D-glucose in L6 myotubes. The pungent phenolic gingerol constituents were identified as the major active compounds in the ginger extract enhancing glucose uptake. (S)-[6]-Gingerol was the most abundant component among the gingerols, however, (S)-[8]-gingerol was the most potent on glucose uptake. The activity of (S)-[8]-gingerol was found to be associated primarily with an increase in surface distribution of GLUT4 protein on the L6 myotube plasma membrane, as detected by expression of hemagglutinin epitope-tagged GLUT4 in L6 muscle cells. The enhancement of glucose uptake in L6 rat skeletal muscle cells by the gingerol pungent principles of the ginger extract supports the potential of ginger and its pungent components for the prevention and management of hyperglycemia and type 2 diabetes.

Culturable endophytes of medicinal plants and the genetic basis for their bioactivity

The bioactive compounds of medicinal plants are products of the plant itself or of endophytes living inside the plant. Endophytes isolated from eight different anticancer plants collected in Yunnan, China, were characterized by diverse 16S and 18S rRNA gene phylogenies. A functional gene-based molecular screening strategy was used to target nonribosomal peptide synthetase (NRPS) and type I polyketide synthase (PKS) genes in endophytes. Bioinformatic analysis of these biosynthetic pathways facilitated inference of the potential bioactivity of endophyte natural products, suggesting that the isolated endophytes are capable of producing a plethora of secondary metabolites. All of the endophyte culture broth extracts demonstrated antiproliferative effects in at least one test assay, either cytotoxic, antibacterial or antifungal. From the perspective of natural product discovery, this study confirms the potential for endophytes from medicinal plants to produce anticancer, antibacterial and antifungal compounds. In addition, PKS and NRPS gene screening is a valuable method for screening isolates of biosynthetic potential.

Modulation of diabetic retinopathy pathophysiology by natural medicines through PPAR-γ-related pharmacology

Diabetic retinopathy (DR) is one of the most common microvascular complications of diabetes and remains a major cause of preventable blindness among adults at working age. DR involves an abnormal pathology of major retinal cells, including retinal pigment epithelium, microaneurysms, inter-retinal oedema, haemorrhage, exudates (hard exudates) and intraocular neovascularization. The biochemical mechanisms associated with hyperglycaemic-induced DR are through multifactorial processes. Peroxisome proliferator-activated receptor-γ (PPAR-γ) plays an important role in the pathogenesis of DR by inhibiting diabetes-induced retinal leukostasis and leakage. Despite DR causing eventual blindness, only a few visual or ophthalmic symptoms are observed until visual loss develops. Therefore, early medical interventions and prevention are the current management strategies. Laser photocoagulation therapy is the most common treatment. However, this therapy may cause retinal damage and scarring. Herbal and traditional natural medicines may provide an alternative to prevent or delay the progression of DR. This review provides an analysis of the therapeutic potential of herbal and traditional natural medicines or their active components for the slowdown of progression of DR and their possible mechanism through the PPAR-γ pathway.

Healing the diabetic heart: modulation of cardiometabolic syndrome through peroxisome proliferator activated receptors (PPARs)

Cardiometabolic syndrome is a mixture of interrelated risk factors predisposing individuals to elevated risk of atherosclerotic cardiovascular disease and type 2 diabetes mellitus. Nuclear receptors, specifically peroxisome proliferator-activated receptors (PPARs), were identified to play a pivotal role in the regulation of metabolic homeostasis. However, with rosiglitazone currently under intense scrutiny great concerns have arisen regarding the safety of the thiazolidinedione PPAR-γ agonist family as a whole. This review discusses the current concern with PPAR-γ agonists by exploring if PPARs can still be considered worth pursuing as a viable target for cardiovascular diseases. We examine current research focusing on identifying ligands that are dual and pan-PPAR agonists, selective PPAR-γ modulators, PPAR-β/δ agonists and that are of natural origin.

Attenuation of liver pro-inflammatory responses by Zingiber officinale via inhibition of NF-kappa B activation in high-fat diet-fed rats

The aim of this study was to investigate whether treatment with a ginger (Zingiber officinale) extract of high-fat diet (HFD)-fed rats suppresses Nuclear factor-kappa B (NF-κB)-driven hepatic inflammation and to subsequently explore the molecular mechanisms in vitro. Adult male Sprague-Dawley rats were treated with an ethanolic extract of Zingiber officinale (400 mg/kg) along with a HFD for 6 weeks. Hepatic cytokine mRNA levels, cytokine protein levels and NF-κB activation were measured by real-time PCR, Western blot and an NF-κB nuclear translocation assay, respectively. In vitro, cell culture studies were carried out in human hepatocyte (HuH-7) cells by treatment with Zingiber officinale (100 μg/mL) for 24 hr prior to interleukin-1β (IL-1β, 8 ng/mL)-induced inflammation. We showed that Zingiber officinale treatment decreased cytokine gene TNFα and IL-6 expression in HFD-fed rats, which was associated with suppression of NF-κB activation. In vitro, Zingiber officinale treatment decreased NF-κB-target inflammatory gene expression of IL-6, IL-8 and serum amyloid A1 (SAA1), while it suppressed NF-κB activity, IκBα degradation and IκB kinase (IKK) activity. In conclusion, Zingiber officinale suppressed markers of hepatic inflammation in HFD-fed rats, as demonstrated by decreased hepatic cytokine gene expression and decreased NF-κB activation. The study demonstrates that the anti-inflammatory effect of Zingiber officinale occurs at least in part through the NF-κB signalling pathway.

Real-Time Translocation and Function of PKCβII Isoform in Response to Nociceptive Signaling via the TRPV1 Pain Receptor

Serine/threonine protein kinase C βII isoform (PKCβII) or the pain receptor transient receptor potential vanilloid 1 (TRPV1) have been separately implicated in mediating heat hyperalgesia during inflammation or diabetic neuropathy. However, detailed information on the role of PKC βII in nociceptive signaling mediated by TRPV1 is lacking. This study presents evidence for activation and translocation of the PKC βII isoform as a signaling event in nociception mediated by activation of TRPV1 by capsaicin. We show that capsaicin induces translocation of cytosolic PKCβII isoform fused with enhanced green fluorescence protein (PKCβII-EGFP) in dorsal root ganglion (DRG) neurons. We also show capsaicin-induced translocation in Chinese Hamster Ovarian (CHO) cells co-transfected with TRPV1 and PKCβII-EGFP, but not in CHO cells expressing PKCβII-EGFP alone. By contrast, the PKC activator phorbol-12-myristate-13-acetate (PMA) induced translocation of PKCβII-EGFP which was sustained and independent of calcium or TRPV1. In addition PMA-induced sensitization of TRPV1 to capsaicin response in DRG neurons was attenuated by PKCβII blocker CGP 53353. Capsaicin response via TRPV1 in the DRG neurons was confirmed by TRPV1 antagonist AMG 9810. These results suggested a novel and potential signaling link between PKCβII and TRPV1. These cell culture models provide a platform for investigating mechanisms of painful neuropathies mediated by nociceptors expressing the pain sensing gene TRPV1, and its regulation by the PKC isoform PKCβII.

The effect of vitamin D3 and ketoconazole combination on VDR-mediated P-gp expression and function in human colon adenocarcinoma cells: implications in drug disposition and resistance

The vitamin D3 metabolite 1,25-dihydroxycholecalciferol (DHC) and analogues derived from it are being investigated as potential agents for the treatment of cancer. Combining ketoconazole (KTZ) with DHC has been recommended to enhance the anticancer activity of DHC. DHC exerts its biological activities through the vitamin D receptor (VDR). VDR is recognized to be a regulator of P-glycoprotein (P-gp), a member of the ABC transporter family well known for its role in multidrug resistance in cancer chemotherapy. We have investigated the effect of DHC and adding KTZ together with DHC on P-gp and VDR expression and the functional consequences of P-gp induction in intestinal human colonic adenocarcinoma cells LS174T cells. DHC increased P-gp expression by two times, and the addition of KTZ further increased the expression to four times. The combination of DHC + KTZ also significantly increased VDR expression, consistent with the enhanced increase in P-gp expression by this combination. The increase in P-gp expression was accompanied by increased P-gp function, as measured by decreased Rh123 accumulation in the LS174T cells. In addition, DHC significantly decreased colchicine cytotoxicity in a dose-sensitive manner, and the addition of KTZ further decreased the colchicine cytotoxicity, indicating the chemo-protective effect of DHC is enhanced by KTZ, consistent with the enhanced expression of P-gp. The results of this study raise the possibility that DHC and the addition of KTZ to DHC treatment may decrease the effectiveness of cancer chemotherapy by promoting P-gp-mediated drug resistance.

Herbal medicines and nutraceuticals for diabetic vascular complications: mechanisms of action and bioactive phytochemicals

Diabetes is one of the most prevalent chronic diseases throughout the world. The majority of its complications arise from vascular-related inflammation apparently initiated by endothelial cell injury. One cause of this injury has been attributed to hyperglycaemia-induced reactive oxygen species. Consequently, current drug developmental strategy has targeted specific inflammatory and oxidative stress pathways for the prevention of diabetic vascular complications. Herbal medicines have traditionally been used for the treatment of diabetes and its complications. In fact, current pre-clinical and clinical studies have demonstrated that many of them exhibit potent anti-inflammatory and anti-oxidative properties, and have also identified the active phytochemicals responsible for their activities. The present review summarises the latest research on the molecular mechanisms of diabetic vascular complications, and evaluates the level of scientific evidence for common herbal medicines and their bioactive phytochemicals. These agents have been shown to be effective through various mechanisms, particularly the NF-κB signalling pathways. Overall, herbal medicines and nutraceuticals, as well as their bioactive components, which exhibit anti-inflammatory and anti-oxidative properties, provide a promising approach for the prevention and treatment of diabetic complications.

Pharmacokinetic and pharmacodynamic interactions of echinacea and policosanol with warfarin in healthy subjects

AIMS

This study investigated the pharmacokinetic and pharmacodynamic interactions of echinacea and policosanol with warfarin in healthy subjects.

METHODS

This was an open-label, randomized, three-treatment, cross-over, clinical trial in healthy male subjects (n= 12) of known CYP2C9 and VKORC1 genotype who received a single oral dose of warfarin alone or after 2 weeks of pre-treatment with each herbal medicine at recommended doses. Pharmacodynamic (INR, platelet activity) and pharmacokinetic (warfarin enantiomer concentrations) end points were evaluated.

RESULTS

The apparent clearance of (S)-warfarin (90% CI of ratio; 1.01, 1.18) was significantly higher during concomitant treatment with echinacea but this did not lead to a clinically significant change in INR (90% CI of AUC of INR; 0.91, 1.31). Policosanol did not significantly affect warfarin enantiomer pharmacokinetics or warfarin response. Neither echinacea nor policosanol had a significant effect on platelet aggregation after 2 weeks of pre-treatment with the respective herbal medicines.

CONCLUSION

Echinacea significantly reduced plasma concentrations of S-warfarin. However, neither echinacea nor policosanol significantly affected warfarin pharmacodynamics, platelet aggregation or baseline clotting status in healthy subjects.

Regulation of low-density lipoprotein receptor and 3-hydroxy-3-methylglutaryl coenzyme A reductase expression by Zingiber officinale in the liver of high-fat diet-fed rats

Zingiber officinale has been used to control lipid disorders and reported to possess remarkable cholesterol-lowering activity in experimental hyperlipidaemia. In the present study, the effect of a characterized and standardized extract of Zingiber officinale on the hepatic lipid levels as well as on the hepatic mRNA and protein expression of low-density lipoprotein (LDL) receptor and 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase was investigated in a high-fat diet-fed rat model. Rats were treated with an ethanol extract of Zingiber officinale (400 mg/kg) extract along with a high-fat diet for 6 weeks. The extract of Zingiber officinale significantly decreased hepatic triglyceride and tended to decrease hepatic cholesterol levels when administered over 6 weeks to the rats fed a high-fat diet. We found that in parallel, the extract up-regulated both LDL receptor mRNA and protein level and down-regulated HMG-CoA reductase protein expression in the liver of these rats. The metabolic control of body lipid homeostasis is in part due to enhanced cholesterol biosynthesis and reduced expression of LDL receptor sites following long-term consumption of high-fat diets. The present results show restoration of transcriptional and post-transcriptional changes in low-density lipoprotein and HMG CoA reductase by Zingiber officinale administration with a high-fat diet and provide a rational explanation for the effect of ginger in the treatment of hyperlipidaemia.

Endophytes and the microbial genetics of traditional medicines

Traditional medicine continues to play an essential role in the healthcare systems of many cultures. In some Asian and African countries up to 80% of the population depend on these ancient and culturally based medicinal practices for their primary healthcare needs. Plants and their derived natural products are frequently employed as traditional medicine and such plants are viewed as attractive targets for the discovery of novel therapeutic agents in natural product investigations. A variety of useful drugs has been discovered following the investigation of traditional herbs, such as morphine (analgesic), digitoxin (cariotonic) and ephedrine (sympathomimetic). These ethnopharmacology approaches to drug discovery are based on the premise that plants used as traditional medicines have shown some form of bioactivity and have the increased likelihood of containing bioactive compounds in comparison to plants selected at random. Three systems of traditional medicine that are relevant to Australian drug discovery researchers include the Chinese, Australian Aboriginal and Indonesian systems.

Protective effects of ethanolic extract of Zingiber officinale rhizome on the development of metabolic syndrome in high-fat diet-fed rats

Metabolic syndrome, including obesity, dyslipidaemia, hyperglycaemia and insulin resistance that predisposes type 2 diabetes is a major disease problem around the world and a plethora of herbal medicines are claimed to be effective in controlling these disorders. The rhizome of Zingiber officinale (Zingiberaceae) is commonly used as a spice in various foods and beverages. Apart from its other traditional medical uses, Z. officinale has been used to control diabetes and dyslipidaemia. In the present study, the protective effects of an ethanolic extract of Z. officinale on the development of metabolic syndrome were investigated in a high-fat diet-fed rat model at doses of 100, 200 and 400 mg/kg body weight. The marked rise in body weights, glucose, insulin, total cholesterol, LDL cholesterol, triglycerides, free fatty acids and phospholipids in serum of the rats that followed 6 weeks of high-fat diet treatment were significantly reduced by Z. officinale treatment. However, no significant change in serum HDL cholesterol was observed either with high-fat diet or Z. officinale compared to both control groups. The present results provide scientific evidence to substantiate the traditional use of Z. officinale in preventing metabolic disorders.

Pharmacodynamic interaction of warfarin with cranberry but not with garlic in healthy subjects

BACKGROUND AND PURPOSE

Patients commonly take complementary medicines in conjunction with warfarin yet evidence supporting the safety or the risk of a herb-drug interaction is lacking. The aim of this study was to investigate the possible impact of two commonly used herbal medicines, garlic and cranberry, on the pharmacokinetics and pharmacodynamics of warfarin in healthy male subjects.

EXPERIMENTAL APPROACH

An open-label, three-treatment, randomized crossover clinical trial was undertaken and involved 12 healthy male subjects of known CYP2C9 and VKORC1 genotype. A single dose of 25 mg warfarin was administered alone or after 2 weeks of pretreatment with either garlic or cranberry. Warfarin enantiomer concentrations, INR, platelet aggregation and clotting factor activity were measured to assess pharmacokinetic and pharmacodynamic interactions between warfarin and herbal medicines.

KEY RESULTS

Cranberry significantly increased the area under the INR-time curve by 30% when administered with warfarin compared with treatment with warfarin alone. Cranberry did not alter S- or R-warfarin pharmacokinetics or plasma protein binding. Co-administration of garlic did not significantly alter warfarin pharmacokinetics or pharmacodynamics. Both herbal medicines showed some evidence of VKORC1 (not CYP2C9) genotype-dependent interactions with warfarin, which is worthy of further investigation.

CONCLUSIONS AND IMPLICATIONS

Cranberry alters the pharmacodynamics of warfarin with the potential to increase its effects significantly. Co-administration of warfarin and cranberry requires careful monitoring.

Salacia oblonga root decreases cardiac hypertrophy in Zucker diabetic fatty rats: inhibition of cardiac expression of angiotensin II type 1 receptor

AIMS

We investigated the effect of the water extract of Salacia oblonga (SOE), an ayurvedic antidiabetic and antiobesity medicine, on obesity and diabetes-associated cardiac hypertrophy and discuss the role of modulation of cardiac angiotensin II type 1 receptor (AT(1)) expression in the effect.

METHODS

SOE (100 mg/kg) was given orally to male Zucker diabetic fatty (ZDF) rats for 7 weeks. At the end-point of the treatment, the hearts and left ventricles were weighed, cardiomyocyte cross-sectional areas were measured, and cardiac gene profiles were analysed. On the other hand, angiotensin II-stimulated embryonic rat heart-derived H9c2 cells and neonatal rat cardiac fibroblasts were pretreated with SOE and one of its prominent components mangiferin (MA), respectively. Atrial natriuretic peptide (ANP) mRNA expression and protein synthesis and [(3)H]thymidine incorporation were determined.

RESULTS

SOE-treated ZDF rats showed less cardiac hypertrophy (decrease in weights of the hearts and left ventricles and reduced cardiomyocyte cross-sectional areas). SOE treatment suppressed cardiac overexpression of ANP, brain natriuretic peptide (BNP) and AT(1) mRNAs and AT(1) protein in ZDF rats. SOE (50-100 microg/ml) and MA (25 micromol) suppressed angiotensin II-induced ANP mRNA overexpression and protein synthesis in H9c2 cells. They also inhibited angiotensin II-stimulated [(3)H]thymidine incorporation by cardiac fibroblasts.

CONCLUSIONS

Our findings demonstrate that SOE decreases cardiac hypertrophy in ZDF rats, at least in part by inhibiting cardiac AT(1) overexpression. These studies provide insights into a potential cardioprotective role of a traditional herb, which supports further clinical evaluation in obesity and diabetes-associated cardiac hypertrophy.

Systematic review on the safety of Harpagophytum preparations for osteoarthritic and low back pain

Harpagophytum products are a treatment option for osteoarthritic and low back pain. The aim of this study was to review the safety of treatment with Harpagophytum procumbens. The databases OVID(MEDLINE), PUBMED and COCHRANE COLLABORATION LIBRARY were searched back to 1985 for studies with Harpagophytum procumbens. Twenty-eight clinical trials were identified of which 20 stated adverse events. In none of the double-blind studies was the incidence of adverse events during treatment with Harpagophytum procumbens higher than during placebo treatment. Minor adverse events occurred in around 3% of the patients, mainly gastrointestinal adverse events. A few reports of acute toxicity were found but there were no reports on chronic toxicity. Since the dosage used in most of the studies is at the lower limit and since long-term treatment with Harpagophytum products is advisable, more safety data are urgently needed.

ThermoTRP channels in nociceptors: taking a lead from capsaicin receptor TRPV1

Nociceptors with peripheral and central projections express temperature sensitive transient receptor potential (TRP) ion channels, also called thermoTRP's. Chemosensitivity of thermoTRP's to certain natural compounds eliciting pain or exhibiting thermal properties has proven to be a good tool in characterizing these receptors. Capsaicin, a pungent chemical in hot peppers, has assisted in the cloning of the first thermoTRP, TRPV1. This discovery initiated the search for other receptors encoding the response to a wide range of temperatures encountered by the body. Of these, TRPV1 and TRPV2 encode unique modalities of thermal pain when exposed to noxious heat. The ability of TRPA1 to encode noxious cold is presently being debated. The role of TRPV1 in peripheral inflammatory pain and central sensitization during chronic pain is well known. In addition to endogenous agonists, a wide variety of chemical agonists and antagonists have been discovered to activate and inhibit TRPV1. Efforts are underway to determine conditions under which agonist-mediated desensitization of TRPV1 or inhibition by antagonists can produce analgesia. Also, identification of specific second messenger molecules that regulate phosphorylation of TRPV1 has been the focus of intense research, to exploit a broader approach to pain treatment. The search for a role of TRPV2 in pain remains dormant due to the lack of suitable experimental models. However, progress into TRPA1's role in pain has received much attention recently. Another thermoTRP, TRPM8, encoding for the cool sensation and also expressed in nociceptors, has recently been shown to reduce pain via a central mechanism, thus opening a novel strategy for achieving analgesia. The role of other thermoTRP's (TRPV3 and TRPV4) encoding for detection of warm temperatures and expressed in nociceptors cannot be excluded. This review will discuss current knowledge on the role of nociceptor thermoTRPs in pain and therapy and describes the activator and inhibitor molecules known to interact with them and modulate their activity.

Molecular and cellular regulators of cancer angiogenesis

Current cancer chemotherapeutic drugs have limited efficacy due to the fact that tumour cells are a rapidly changing target characterised by genomic instability. Unlike tumour cells, activated endothelial cells (ECs) required for angiogenesis, a process indisputably crucial to tumour growth and metastasis, were originally considered to be ideal therapeutic targets free of drug resistance. Additionally, unlike preclinical studies in mice using inhibitors targeting the powerful EC mitogen--vascular endothelial growth factor (VEGF)--overall survival benefit with anti-VEGF therapy used as monotherapy has yet to be demonstrated in phase III clinical trials. In contrast, VEGF-specific antibodies combined with current chemotherapy have resulted in improved outcomes in certain previously untreated cancers. This has led some researchers to hypothesize that combined treatments targeting other angiogenic molecules besides VEGF, and/or targeting not only ECs but other angiogenic non-EC types, may offer alternative but effective therapeutic options for eradicating malignant tumours. A rational approach to effective anti-angiogenic combination therapy will, however, require further understanding of the molecular and cellular mechanisms which undergird tumour vascularisation. Recent studies involving judicious use of powerful new genetic approaches have provided unprecedented insights into how different molecular and cellular mechanisms cooperate to build, branch and mature the growing vessel network so pivotal to tumour growth and survival. This review covers our current understanding of how the various key players--the tumour cells, stromal cells, endothelial cells and pericytes, and bone-marrow-derived haematopoietic and putative endothelial progenitors interact via their cell-derived pro- or anti-angiogenic factors to regulate tumour angiogenesis.

Pomegranate flower: a unique traditional antidiabetic medicine with dual PPAR-alpha/-gamma activator properties

PPARs are transcription factors belonging to the superfamily of nuclear receptors. PPAR-alpha is involved in the regulation of fatty acid (FA) uptake and oxidation, inflammation and vascular function, while PPAR-gamma participates in FA uptake and storage, glucose homeostasis and inflammation. The PPARs are thus major regulators of lipid and glucose metabolism. Synthetic PPAR-alpha or PPAR-gamma agonists have been widely used in the treatment of dyslipidaemia, hyperglycaemia and their complications. However, they are associated with an incidence of adverse events. Given the favourable metabolic effects of both PPAR-alpha and PPAR-gamma activators, as well as their potential to modulate vascular disease, combined PPAR-alpha/-gamma activation has recently emerged as a promising concept, leading to the development of mixed PPAR-alpha/-gamma activators. However, some major side effects associated with the synthetic dual activators have been reported. It is unclear whether this is a specific effect of the particular synthetic compounds or a class effect. To date, a medication that may combine the beneficial metabolic effects of PPAR-alpha and PPAR-gamma activation with fewer undesirable side effects has not been successfully developed. Pomegranate plant parts are used traditionally for the treatment of various disorders. However, only pomegranate flower has been prescribed in Unani and Ayurvedic medicines for the treatment of diabetes. This review provides a new understanding of the dual PPAR-alpha/-gamma activator properties of pomegranate flower in the potential treatment of diabetes and its associated complications.

Specific reversal of multidrug resistance to colchicine in CEM/VLB(100) cells by Gynostemma pentaphyllum extract

P-glycoprotein (P-gp)-mediated multiple drug resistance (MDR) is perhaps the most thoroughly studied cellular mechanism of cytotoxic drug resistance. Its efflux function can be circumvented by a wide range of pharmacological agents in vitro and in vivo. Most of these agents are pharmaceuticals used clinically for conditions other than cancer. However, their use in alleviating MDR is limited because the concentrations required for inhibition of the pump surpass their dose-limiting toxicity. The aim of this research is to study the role of gypenosides, isolated from Gynostemma pentaphyllum, as modulators of P-gp-mediated MDR in tumor cells, at both cellular and plasma membrane level. In the presence of total gypenoside preparation (0.1 mg/ml), an approximately 15-fold reversal of colchicine (COL) resistance was observed in P-gp-overexpressed CEM/VLB(100) cells. However, the gypenoside sample showed no reversal effect in cells treated with vinblastine and taxol. A purified gypenoside sample (gypenoside fraction 100) exhibited even more significant reversal of COL resistance (approximately 42-fold) in the CEM/VLB(100) cells. Further examination of the reversal effect of fraction 100 in membrane vesicles derived from CEM/VLB(100) cells using the continuous fluorescence method found that gypenoside fraction 100 at 0.1 mg/ml completely abolished the transport of fluorescein-COL.